package ZuoYe.java;

public class Yuan {
	int r;

	public double zhouchang() {
		double a = 3.14 * 2 * r;
		return a;
	}

	public static void main(String[] args) {
		Yuan b = new Yuan();
		b.r = 3;
		double d = b.zhouchang();
		System.out.println(d);
	}
}
